The construction sector is facing industrial disruption from Wednesday as crane drivers belonging to Unite prepare to strike in a dispute over pay.
Unite says it represents 90% (around 170) of Ireland's crane drivers, though that figure is disputed by SIPTU, which has traditionally represented the grade.
SIPTU has lodged a formal complaint against Unite with the Irish Congress of Trade Unions for recruiting the crane drivers.
That complaint will be heard tomorrow.
Unite is pursuing a 10% pay claim for the crane drivers that would bring their hourly rate to around €24 from 1 January 2017, €27 from 1 January 2018 and €30 from 1 January 2019.
However, both union and management sources say that this claim would distort the relativities between pay scales for up to 14,000 general operatives represented by SIPTU.
Last month, SIPTU signed an agreement with the Construction Industry Federation that would give crane drivers two hours extra pay per day for "greasing time" to lubricate the cables on their cranes.
Unite has already balloted crane drivers working on sites belonging to seven firms which do not belong to the CIF, and which the union claims have refused to engage with them on their grievances.
Those intermittent rolling strikes will hit a number of sites from Wednesday.
Unite has now pledged to ballot members on CIF sites, with nationwide industrial action possible from 13 July.
Unite official Tom Fitzgerald said a strike by crane drivers would have a massive effect on productivity on sites, particularly as other construction workers would probably refuse to pass the Unite picket.
The CIF confirmed that Unite had served notice of industrial action, adding that it continued to request that all issues be dealt with through established processes and protocols.
A construction industry source acknowledged that any such stoppage of crane drivers could have massive consequences on numerous sites with implications for a number of key projects.
Meanwhile, the CIF and construction unions including both SIPTU and Unite attended the Labour Court today to discuss the possibility of agreeing a Sectoral Employment Order to establish legally binding pay framework for the sector.